The objectives of this investigation are to establish conditions for the maintenance of rodent lung in vitro as an organ explant and to employ this organ culture model to study the regulation of dipalmitoyl phosphatidyl cholin (DPPC) synthesis, storage and secretion as it relates to the "surfactant system" of the lung. Explants of lung tissue from adult and fetal mice will be placed in Trowell's T-8 culture medium which also contains fluorocarbon FC-47 as an oxygen carrier. Careful evaluation of the many variables associated with organ culture will be made, for example pH, osmolality, hormones, vitamins, gaseous environment. Tissue in culture will be evaluated histologically by light and electron microscopy as well as histochemically. Biochemical assessment of tissue viability will include oxygen uptake, glucose conversion to CO2 and lactic acid as well as glucose, glycerol and acetate conversion to lipids. Detailed studies on the ability of lung in culture to synthesize DPPC and the regulatory aspects of this synthesis will be investigated by radioisotope techniques and specific enzyme analysis. Embryonic lung explants will be studied in terms of their ability to continue differentiation in vitro and to become capable of DPPC synthesis and "surfactant" production.